FIG. 1 shows a traditional process historian system that includes a controller 10, a data server 12, an interface node 14, and a historian database or repository 16. Typically, an event timestamp is applied at the interface node 14. Interface nodes 14 collect, interrogate, and qualify information provided by the data server 12. If the data values collected at the interface node 14 exceed pre-defined dead band thresholds, a timestamp is applied, and the data is transferred to the historian repository 16. If the data does not exceed the threshold, the data point is disregarded and not archived. This process is better known as exception testing.
In the system shown in FIG. 1, the event that is passed to the interface node 14 is value based, not time driven. That is, the controller 10 does not provide a timestamp to the data server 12, but only a process value. This procedure for collecting and timestamping data does not work well for events that are time stamped at the source device such as an Intelligent Electronic Devices (IED). After the IED has determined that an exception has occurred, a timestamp is generated by IED and applied to the event before the data is transmitted to the process historian system. Using a value-based exception reporting such as that shown in FIG. 1 will not transfer meaningful timestamps from the IED to the historian repository 16.